The objective of this project is to develop a better understanding of ligamentous injuries of the wrist. The diagnosis of wrist ligament injuries increases yearly and they are now as common as carpal tunnel syndrome. At our present knowledge of the pathomechanics, early diagnosis and treatment are limited and inconsistent. The information gained from this project will help determine the relative importance of several wrist ligaments. Based upon this information, a non-invasive imaging study will be developed to accurately predict if specific ligaments are injured. In addition, several ligament reconstructions will be tested biomechanically to determine their effectiveness. This information will allow the clinician to treat this problem with a much higher likelihood of success. This project has four specific aims. The first aim is to evaluate the effect of injury to three specific ligaments in various combinations, on the stability of the scaphoid and lunate. The results of this study will allow a determination of the function of these ligaments on the scaphoid and lunate. The second aim of the project is to develop a method to quickly and accurately evaluate patients with wrist ligament injuries. Biomechanical data derived from the first portion of the experiment will be analyzed three-dimensionally to determine the optimal wrist position to radiographically detect changes in carpal bone position following ligament injury. These changes in carpal bone location can be detected by CT scans with the wrist placed in a specific position. It is our hypothesis that injury to a ligament or combination of ligaments results in changes in the orientation of the scaphoid and lunate at specific wrist positions, which are unique to that specific combination of ligament injuries. The third aim is to clinically validate the findings of the second aim. A prospective study of patients undergoing surgery for ligament injuries to the scaphoid and lunate will be performed. CT scans will be obtained of the injured wrist in specific positions and predictions as to which ligaments are torn will be made. Surgical exploration will then ascertain the integrity of the ligaments and validate the predictions. The fourth aim is to biomechanically evaluate two commonly performed surgical reconstructions for instability between the scaphoid and lunate and to determine if carpal stability is restored.